Re: [PATCH 1/3] [media] mt9v032: Add reset and standby gpios

[Markus Pargmann <mpa-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

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Hi,

On Monday 09 November 2015 14:28:56 Laurent Pinchart wrote:
> Hi Markus,
> 
> Thank you for the patch.
> 
> On Friday 06 November 2015 14:13:43 Markus Pargmann wrote:
> > Add optional reset and standby gpios. The reset gpio is used to reset
> > the chip in power_on().
> > 
> > The standby gpio is not used currently. It is just unset, so the chip is
> > not in standby.
> 
> We could use a gpio hog for this, but given that the standby signal should 
> eventually get used, and given that specifying it in DT is a good hardware 
> description, that looks good to me.
> 
> > Signed-off-by: Markus Pargmann <mpa-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
> > Reviewed-by: Philipp Zabel <p.zabel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
> > ---
> >  .../devicetree/bindings/media/i2c/mt9v032.txt      |  2 ++
> >  drivers/media/i2c/mt9v032.c                        | 23 +++++++++++++++++++
> >  2 files changed, 25 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/media/i2c/mt9v032.txt
> > b/Documentation/devicetree/bindings/media/i2c/mt9v032.txt index
> > 202565313e82..100f0ae43269 100644
> > --- a/Documentation/devicetree/bindings/media/i2c/mt9v032.txt
> > +++ b/Documentation/devicetree/bindings/media/i2c/mt9v032.txt
> > @@ -20,6 +20,8 @@ Optional Properties:
> > 
> >  - link-frequencies: List of allowed link frequencies in Hz. Each frequency
> > is expressed as a 64-bit big-endian integer.
> > +- reset-gpios: GPIO handle which is connected to the reset pin of the chip.
> > +- standby-gpios: GPIO handle which is connected to the standby pin of the
> > chip.
> > 
> >  For further reading on port node refer to
> >  Documentation/devicetree/bindings/media/video-interfaces.txt.
> > diff --git a/drivers/media/i2c/mt9v032.c b/drivers/media/i2c/mt9v032.c
> > index a68ce94ee097..4aefde9634f5 100644
> > --- a/drivers/media/i2c/mt9v032.c
> > +++ b/drivers/media/i2c/mt9v032.c
> > @@ -24,6 +24,7 @@
> >  #include <linux/videodev2.h>
> >  #include <linux/v4l2-mediabus.h>
> >  #include <linux/module.h>
> > +#include <linux/gpio/consumer.h>
> 
> module.h escaped my vigilance, but let's try to keep headers alphabetically 
> sorted.
> > 
> >  #include <media/mt9v032.h>
> >  #include <media/v4l2-ctrls.h>
> > @@ -251,6 +252,8 @@ struct mt9v032 {
> > 
> >  	struct regmap *regmap;
> >  	struct clk *clk;
> > +	struct gpio_desc *reset_gpio;
> > +	struct gpio_desc *standby_gpio;
> > 
> >  	struct mt9v032_platform_data *pdata;
> >  	const struct mt9v032_model_info *model;
> > @@ -312,16 +315,26 @@ static int mt9v032_power_on(struct mt9v032 *mt9v032)
> >  	struct regmap *map = mt9v032->regmap;
> >  	int ret;
> > 
> > +	gpiod_set_value_cansleep(mt9v032->reset_gpio, 1);
> > +
> >  	ret = clk_set_rate(mt9v032->clk, mt9v032->sysclk);
> >  	if (ret < 0)
> >  		return ret;
> > 
> > +	/* system clock has to be enabled before releasing the reset */
> 
> Nitpicking, the driver capitalizes the first letter of comments.
> 
> >  	ret = clk_prepare_enable(mt9v032->clk);
> >  	if (ret)
> >  		return ret;
> > 
> >  	udelay(1);
> > 
> > +	gpiod_set_value_cansleep(mt9v032->reset_gpio, 0);
> > +
> > +	/*
> > +	 * After releasing reset, it can take up to 1us until the chip is done
> > +	 */
> > +	udelay(1);
> > +
> 
> The delay isn't necessary if there's no reset GPIO. How about
> 
> 	if (mt9v032->reset_gpio) {
> 		gpiod_set_value_cansleep(mt9v032->reset_gpio, 0);
> 
> 		/* After releasing reset, it can take up to 1us until the
> 		 * chip is done.
> 		 */
> 		udelay(1);
> 	}
> 
> And, according to the datasheet, the delay is 10 SYSCLK periods. 1µs should be 
> safe as the minimum SYSCLK frequency is 13 MHz. I'd still mention it in a 
> comment, maybe as
> 
> 		/* After releasing reset we need to wait 10 clock cycles
> 		 * before accessing the sensor over I2C. As the minimum SYSCLK
> 		 * frequency is 13MHz, waiting 1µs will be enough in the worst
> 		 * case.
> 		 */
> 		udelay(1);
> 
> If you're fine with these changes there's no need to resubmit the patch, I can 
> fix it when applying it to my tree.

Thanks, I am fine with all your changes. But as there will be a v2 for the
other two patches I could as well send an updated version if you wish.

Thanks,

Markus

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